Eric Drexler and Ralph Merkle purport to be alchemists of the modern age, manipulating atoms to transform matter. They call it nanotechnology , and say it will cure cancer and create beef without cows. Not everyone believes them. But to sceptics they say, you never thought you'd see a man in t he moon
Eric Drexler and Ralph Merkle do not look like men with a vision which could change the world. Fortysomething, with thinning hair and expanding waistlines, they could be school teachers or civil servants. Instead, the two friends are the driving force behind a science known as nanotechnology. And nanotechnology is a kind of modern day alchemy.

Simply put, Drexler and Merkle are attempting to make tools which can rearrange atoms, the very building blocks of nature, as if they were toying with a tiny Lego set. They are convinced that working on such an unimaginably tiny scale is not only possible, but that once we can put together atoms like Lego bricks, almost nothing is impossible.

Pure and perfect diamonds could be created out of coal in a matter of minutes, steak synthesised out of grass and water, cancerous cells repaired by minute robotic surgeons injected into the blood stream. Entire products like cars or computers could be built from scratch, one atom at a time. Even death itself might no longer be inevitable, since nanotechnology's atomic-scale dexterity would include the ability to repair cells damaged by the ageing process.

"People often say this sounds like science fiction,'' says Drexler. "And I say, `Do you mean like rockets to the moon, or robots, or talking computers? They were all in science fiction first.'''

K Eric Drexler is Mr Nanotechnology, the inventor of the term and founder of a scientific think tank, the Foresight Institute, which is devoted to pushing out the boundaries of the science. Far fetched as they may sound, his prophesies are not the ranting of a lunatic but the result of years of scientific study. He travels all over the world lecturing fellow scientists on his subject, and has written three books including The Engine of Creation (1986), the "bible" of nanotechnology. In Japan, Drexler is a frequent visitor and a minor celebrity. Television shows and magazines are dedicated to his extraordinary vision of the future, and the minister of international trade and industry is investing upwards of $200 million in a purpose-built nanotechnology centre just outside Tokyo. In America, Fortune magazine has tipped nanotechnology as having "spectacular" long-term potential for adventurous investors. And at Xerox PARC, the photocopy company's research centre south of San Francisco, Ralph Merkle heads a small unit exploring nanotechnology's implications for computers.

Drexler is precise, slightly pompous and a touch impatient. A ferociously intelligent man, he is a visiting lecturer at Stanford and has a doctorate from the Massachusetts Institute of Technology. With his thick spectacles and sickly, pale complexion, he is a typical boffin, with an atypical combination of limitless imagination and unerring logic.

Ralph Merkle, his long-standing sidekick, has a Stanford PhD in electrical engineering and an international reputation in the field of secret military codes, and he now heads what's called Xerox's Computional Nanotechnology Project. A giant of a man, he is more affable and out-going than his partner, with an almost paternalistic way of explaining the unexplainable.

The heart of their theory is atoms. All matter is made of them. And, the thinking goes, if we can find a way to manipulate and move atoms into any patterns and structures we want, we can synthesise anything, solve any problem, make any product at minimal financial and environmental cost.

Mankind, Drexler points out, has been manipulating atoms ever since he carved an axe out of a piece of flint. He does so when he mixes chemicals to create new compounds, or bends steel to create a car. But, in the future, the control will be more exact, the process more precise, the results infinitely more spectacular. Never one to understate his case, Drexler equates the power of nanotechnology with the introduction of agriculture or industry.

Sorting through the debris in his tiny, cluttered office, Merkle emerges with a primitive cardboard-and-string contraption and attempts to explain how, one day, something like it might help mankind gain complete "control over the structure of matter", the fundamental promise of nanotechnology.

The construction, he stresses, is only a model, a crude demonstration device. In reality it would be made of "some kind of diamond structure, or possibly a protein". It would have some form of robotic arm attached to it, and would be capable of physically grasping an individual atom and moving it to a new location. And it would be smaller; much, much smaller. How small, exactly?

"Ooooh," says Drexler, "I don't know. Maybe a tenth of a micron." That's smaller than many viruses, visible only with the most powerful microscope. Something like one six-hundredth of the diameter of a human hair. So inconceivably small that you could fit about 60 million of the little implements in a square inch. Small enough, that is, to pick up and move atoms.

It would not, Drexler emphasises, work alone. The first thing this minuscule machine would be instructed to make would be a copy of itself. The copy would then make a copy, and so on. Pretty soon there would be a vast army of millions of machines. This is not unlike the way nature works, says Drexler, pointing to the way bacteria, for instance, multiply by reproducing copies of themselves. "Every time someone makes yoghurt, he's demonstrating how self-replicating molecular machines work."

Drexler and Merkle call their hypothetical gadgets "universal assemblers", and are convinced that one day they will replace factories and assembly lines with miniature manufacturing systems operating at the scale of atoms.

In fact, the notion of such atomic engineer-ing was around long before there was nano- technology. In 1959, when Eric Drexler was little more than a toddler, Richard Feynman, the Nobel Prize-winning physicist and co-inventor of the atomic bomb, gave a lecture called "There's More Room at the Bottom". In it he presented a scientifically feasible scenario of how all of human knowledge could be written in a cube smaller than a speck of dust. Moreover, Feynman insisted, "the principles of physics, as far as I can see, do not speak against the pos-sibility of manoeuvering things atom by atom." Now that possibility is becoming practical.

Drexler is at the forefront of this realisation. When he was 19 (and something of a scient- ific whizz kid), he published a modest paper entitled "Space Colony Supply from Asteroidal Materials". As a student of new manufacturing techniques, he was worried about the dwindling resources on earth and fascinated by the prospect of mining the infinite supply of raw materials in outer space. But when the genetic engineering industry started to expand, Drexler realised that if mankind could mimic DNA, nature's main manufacturing method, running out of resources would be less of a problem.

"I asked myself the question, `What can we do when we learn how to design and build molecular machine systems that are similar to the molecular systems we find in cells?'' he recalls.

Although unaware of Feynman's predictions, the young Eric started wondering what would happen if scientists could make tiny machines like those found in nature; machines which could rearrange atoms and build new products.

Nature, after all, is brimming over with examples of molecular machines. A tree, for instance, builds its leaves and wood out of carbon dioxide, water and light. Man himself is an example of molecular machines at work, an immensely complex organism built from a single cell and a strand or two of DNA.

But if it is nature which inspires Drexler's imagination, it is the quest for ever more powerful computers that is pushing forward nano-scale research. More power means more memory, which requires smaller microchips. Without these, computing innovations will grind to a halt; and there is a limit to how small we can make chips out of silicon as we do now.

"There's a lot of debate about when we will hit that wall," says Merkle, "but it is generally agreed that it will be in about ten years. When that happens, either the computer revolution ends or we find alternative technology."

That will mean making chips with circuits made up of "wires" just a few atoms wide, and explains why Xerox, IBM, Hitachi, and other computer companies are so interested in nano-technology. Ultimately, Drexler suggests, a computer the size of a virus could be as powerful as today's PCs.

"Assuming we progress at the current rate," Merkle adds, "we will have computer memories which store one bit of digital information in one atom somewhere around the year 2020. A technology that lets you put every atom in the right place is essential for the ultimate in miniaturisation of electronics - and it will also let us build a broad range of other products less expensively and more precisely."

Today there are biologists in Utah, chemists in Birmingham and engineers in Tokyo, all making their own independent scientific ex- plorations into doing just that: putting every atom in the right place. Only seven years after Bell Laboratories engineers, using a Scanning Tunnelling Microscope (STM), became the first men to pick up and isolate a single atom, we can now operate at this infinitesimal scale with a surprising degree of control.

As visible proof, a number of researchers have created what's been called "nano-art", using the ultra fine tip of an STM like an atomic paintbrush, creating tiny images constructed out of a handful of individual atoms. When researchers at Hitachi spelled out "Peace '91" in sulphur atoms, the 1 of the 91 was only one atom wide. IBM made the cover of Time magazine when their researchers wrote out the company's logo using the same technique.

Don Eigler, the man responsible for that remarkable feat, has since created an atomically manufactured carbon monoxide molecule, the world's first substance created with nanotechnology. He did it by using an STM to push one carbon atom and one oxygen atom together.

Bit by bit, other scientists from diverse disciplines are making discoveries which might one day form part of a ``universal assembler'' as Drexler and Merkle envisage. David Blair, a biologist at the University of Utah, is studying a bacteria which acts like a motor, spinning nature's equivalent of a drive shaft at 15,000 rpm. In England, Dr Fraser Stoddart, a chemist at Birmingham University, has made a molecule which acts like an electrical switch.

Last year Dr Jack Gibbons, director of the Office of Science and Technology Policy at the White House, told the National Conference on Manufacturing Needs of US Industry that "nanotechnology has become engineering practice. Precise atomic and molecular control in the synthesis of solid-state three-dimensional nanostructures is now possible." Nor was that all. "The stage is being set for actual manufacture of a wide variety and range of custom-made products based on the ability to manipulate individual atoms and molecules during the manufacturing process."

So where do Drexler and Merkle fit into the picture? Apart from being the inventors and most vociferous proponents of the theory, they are the unofficial figureheads of the nanotechnology movement, co-ordinators of a loosely knit global network of scientists. Later this year, at a conference organised by Drexler's Foresight Institute, nano- enthusiasts will gather to discuss the latest developments. Many are computer professionals from Silicon Valley who believe in Drexler's theories with an almost evangelical zeal. Others are scientists who are making practical, if piecemeal, progress towards turning their dream into reality.

On a high-powered computer, Drexler and Merkle have begun designing what one day might be the components for their beloved ``universal assembler''. Using a simulation programme which creates models of atomic structures, they have designed, atom by atom, a tiny wheel cylinder and universal joint, which exist only in the computer's memory but, they say, prove once and for all that such structures can theoretically be built.

"The problem", says Merkle, "is that this workstation handles five- or ten-thousand atoms. A complete assembler would require hundreds of thousands of atoms. We need more than two researchers and one workstation. Given more resources, it would be simple to complete the design." He grins sheepishly. "Of course, building it for real is another matter."

Both men are now more sure than ever that their grandiose ideas will work in practice.

"The questions I get asked now are not so much If? as When? and How?" says Drexler. "The big question is the time-frame. I would say that by the early-21st century we will have some form of molecular manufacturing."

Nevertheless, some critics still insist that just because nanotechnology is feasible does not make it inevitable. Drexler prefers the mantra ``If it can be done, it will be done'', but at times he is his own worst enemy, unable to resist bludgeoning people with the more wildly imaginative conclusions he draws from his theories.

Take, for instance, a device known in nano-circles as ``the meat machine''. Drexler sees no reason why a box containing millions of atomic assemblers should not convert grass, water and nutrients into prime beef - without the inconvenience of a cow.

Not surprisingly, claims like this upset conservative scientists hungry for hard facts rather than grand visions. Edward Wolf, the former head of the National Nanofabrication Facility at Cornell University, warns that "nanotechnology has been oversold" and believes the more earth-shattering benefits are too far off to warrant thinking about. Philip Barth, a micro- device developer at Hewlett Packard, has called Drexler a "flake" for concentrating on bringing his ideas to mass attention rather than publishing academic papers.

Eric Drexler is unrepentant. What holds America back, he counters, is technological myopia, a refusal to invest in the long term.

"Xerox has a ten-year planning horizon, which by corporate American standards is very good," explains Merkle. "In Japan, Hitachi, for instance, look 50 years ahead."

"Successful world leaders have long-term horizons," adds Drexler bitterly. ``Dogs and cats have short-term horizons. I often wonder why it's better to be closer to the dogs and cats.

"Some people are assuming that the future will be the same as it is today. That's been a pretty good rule of thumb in the past. But," he chuckles, "it seems that there are going to be some changes ..."